KR20030045647A - Method for transitioning between ziegler-natta and metallocene catalysts in a bulk loop reactor for the production of polypropylene - Google Patents

Abstract

PURPOSE: A method for polymerizing propylene in a bulk loop reactor, a method for contacting a metallocene flow with a propylene flow and a method for introducing an antifouling agent into a bulk loop reactor are provided, to produce commercial amount of polypropylene by transitioning between Ziegler-Natta and metallocene catalysts in a bulk loop reactor. CONSTITUTION: The polymerization method of propylene in a bulk loop reactor having a first temperature range comprises the steps of introducing a certain quantity of a metallocene catalyst having a second temperature range from a first catalyst mixing system connected with a bulk loop reactor into the bulk loop reactor with a first frequency; and introducing a certain quantity of a Ziegler-Natta catalyst having a third temperature range from a second catalyst mixing system connected with the bulk loop reactor into the bulk loop reactor with a second frequency. Preferably the first frequency is hither than the second frequency, and the first temperature range is higher than the second temperature range.

Description

TECHNICAL FOR TRANSITIONING BETWEEN ZIEGLER-NATTA AND METALLOCENE CATALYSTS IN A BULK LOOP REACTOR FOR THE PRODUCTION OF POLYPROPYLENE}

Related Applications

This application claims the benefit of US application Ser. No. 60 / 336,801, filed December 3, 2001, entitled "Method for Transitioning Between Ziegler-Natta and Metallocene Catalyst in a Bulk Loop Reactor for the Production of Polypropylene".

Scope of Invention

The present invention relates generally to the production of polypropylene and polypropylene copolymers and in particular to the production of such polymers in bulk loop reactors.

Background of the Invention

Polypropylene and polypropylene copolymers are formed in the polymerization reactor in the presence of a suitable catalyst. Propylene monomers, either alone or together with one or more other monomers, such as ethylene, are introduced into the reactor to produce polypropylene homopolymer or copolymer fluff, and granules. The propylene polymer is discharged from the reactor, subjected to appropriate processing, and then extruded into a thermoplastic material through an extruder and a die mechanism to produce the propylene polymer as a raw material, usually in a special form such as pellets. The propylene polymer pellets are finally heated and processed into the form of the desired end product. Examples of such end products include fibers, webs (woven or non-woven), films, pipes, containers and shaped articles. Other examples of such products made of propylene polymers include components of durable articles such as automotive interior and exterior components, and home interior and exterior components.

One type of reactor suitable for the production of polypropylene homopolymers and copolymers is a bulk loop reactor. The bulk loop reactor may be formed of one or more interconnected loops with continuous lumen. The catalyst is dispersed by circulating the liquid propylene monomer in a continuous lumen. In this way, propylene polymer polymerization occurs in continuous lumen. Two or more bulk loop reactors may be connected in series, for example. In this way, in order to achieve the desired polymer properties, the polymerization conditions of each reactor may be the same or different. Examples of polymerization conditions that may vary are temperature, pressure, monomer content, co-monomer content, catalyst, co-catalyst and hydrogen concentration.

The polymer particles leaving the bulk loop reactor may be subjected to the above processing process, or may be introduced into one or more polymerization reactors, for example one or more gas phase reactors, to further polymerize with other monomers, for example ethylene, to physics of the propylene polymer resin. And chemical properties can be modified. In addition, the physical and chemical properties of the propylene polymer resin can be adjusted by the selection of one or more catalyst systems. Bulk loop reactors can produce from 1 to at least 50 tonnes of propylene polymer per hour for substantially continuous and at high yields for extended time, for example for periods of five to two years and longer. This provides several advantages over other types of propylene reactors, such as stirred pots, stirred phases and other non-substantially continuous reactors. However, while there may be catalyst systems useful for the production of one or more propylene, in some instances the presence of small amounts of one catalyst system or small amounts of one or more of its components may interfere with each other or interfere with the performance of other catalyst systems. As such, although there are several catalyst systems useful for the production of polypropylene, not all such catalyst systems are compatible in combination with each other. Moreover, although the design and / or physical environment and associated equipment in the bulk loop reactor are suitable for the production of polypropylene using one catalyst system, these conditions and / or designs are less suitable for the production of polypropylene using another catalyst system, or It may be less desirable. Therefore, in order to take advantage of the advantages provided in bulk loop reactors, such problems need to be avoided when using different catalyst systems in conventional bulkfur reactors producing propylene polymers.

Summary of the Invention

FIELD OF THE INVENTION The present invention relates to propylene polymerization processes in bulk loop reactors, and more particularly to propylene polymerization processes for polymerizing polypropylene in commercial quantities in bulk loop reactors. In one embodiment, there is provided a propylene polymerization process in a bulk loop reactor by injecting a metallocene catalyst and a Ziegler-Natta catalyst system under propylene polymerization conditions. In this embodiment, the bulk loop reactor has a first temperature range. An amount of metallocene catalyst having a second temperature range is introduced into the bulk loop reactor at a first frequency rate from the first catalyst mixing system in communication with the bulk loop reactor. An amount of Ziegler-Natta catalyst having a third temperature range is introduced into the bulk loop reactor at a second frequency from a second catalyst mixing system in communication with the bulk loop reactor. In this embodiment, the first frequency is higher than the second frequency and the first temperature range is higher than the second temperature range.

In another embodiment, a certain amount of supported metalphosne catalyst is contacted with a first amount of scavenger, and the Ziegler-Natta catalyst is bulk looped before injecting the supported metallocene catalyst under the propylene polymerization conditions into the bulk loop reactor. A certain amount of Ziegler-Natta catalyst is contacted with a second amount of scavenger prior to injection into the reactor, where the second amount of scavenger is provided in a bulk loop reactor with a propylene polymerization method that is larger than the first amount of scavenger do. In this embodiment, the scavenger may be TEAL.

In another embodiment, a method of contacting a flow of metallocene with a flow of propylene is provided. This method involves directing the flow of metallocene to the junction, directing the flow of propylene to the junction, partial flow of metallocene separated from a portion of the propylene stream, and at a distance to the junction of the downstream propylene stream. Maintenance. In this embodiment, the temperature of the metallocene stream or propylene stream may be from −10 ° C. to + 10 ° C. In this embodiment, the flow rate downstream of the junction can be 0.3 m / sec to 10 m / sec.

In another embodiment, a method of introducing a volume of antifouling agent into a catalyst mixing system is provided. In this embodiment, a portion of the antifouling agent is introduced at or near the point where the propylene stream and the stream of catalyst contact. The antifouling agent may be a member kneaded with a single or other member selected from the group consisting of Stadis 450 conductivity enhancer, Synperonic, and Pluronic.

1 is a schematic plan view of a bulk loop reactor system in combination with a gas phase reactor.

2 is a top view of another bulk loop reactor.

3 is a schematic plan view of a loop reactor element of a bulk loop reactor system.

3A is a plan view of a catalyst mixing and injection system.

3B is a top view of another catalyst mixing and injection system.

4 is a cross-sectional view of the conduit junction containing the propylene and catalyst and showing the quill.

Detailed description of the invention

Conventional Ziegler-Natta Catalysts

Traditionally, bulk for commercial production of polypropylene homopolymers and / or copolymers (in the range of 1 to 5 tonnes per hour, preferably at least 1 to at least 50 tonnes polymer per hour for a period of at least 5 days to at least about 2 years) Catalyst systems used in loop reactors are commonly known as Ziegler-Natta catalyst systems (hereinafter may be referred to as "Ziegler-Natta catalysts" or "Ziegler-Natta catalyst systems"). Suitable conventional Ziegler-Natta catalysts are described, for example, in US Pat. No. 4,701,431 (see, in particular, 5 lines of 27 columns to 6 columns of 5); 4,987,200 (see, in particular, 22 lines of 27 columns to 17 lines of 28 columns); 3,867,920; 4,086,408; 4,376,191; 5,019,633; 4,482,687; 4,101,445; 4,560,671; 4,719,193; 4,755,495; And 5,070,055, each of which is incorporated herein by reference in its entirety. These Ziegler-Natta catalyst systems can include Ziegler-Natta catalysts, supports, one or more internal donors, one or more external donors.

Typical Ziegler-Natta catalysts are stereospecific, formed from transition metal halides and metal alkyls or halides, and are capable of producing isotactic polypropylene. Ziegler-Natta catalysts are derived from metal halides and / or metalalkyls, typically organoaluminum compounds, as halides and cocatalysts of transition metals such as titanium, chromium or vanadium. The catalyst typically consists of a titanium halide supported on a magnesium compound. Ziegler-Natta catalysts, such as active magnesium halides, for example titanium tetrachloride supported on magnesium dichloride or magnesium dibromide, are described, for example, in US Pat. Nos. 4,298,718 and 4,544,717 to Mayr et al. Supported catalysts disclosed in the call. Silica can also be used as a support. Supported catalysts can be used with promoters such as alkylaluminum compounds such as triethylaluminum (TEAL), trimethylaluminum (TMA), and triisobutyl aluminum (TIBAL).

Conventional Ziegler-Natta catalysts may be used with one or more internal electron donors. These internal electron donors can be added during the preparation of the catalyst and can be combined with the support or combined with other transition metal halides. Suitable Ziegler-Natta catalysts containing diether-based internal donor compounds are those available as Mitsui RK-100 and Mitsui RH-220 manufactured by Mitsui Chemicals, Inc. of Japan. The RK-100 catalyst additionally includes an internal phthalate donor. Ziegler-Natta catalysts are typically supported catalysts. Suitable support materials include magnesium compounds such as magnesium halides, dialkylmagnesium, magnesium oxide, magnesium hydroxide, and magnesium carboxylates. Typical magnesium levels are from about 12% to 20% of the catalyst weight. The RK-100 catalyst comprises about 2.3 weight percent titanium, approximately 17.3% of magnesium weight. The RH-220 catalyst comprises about 3.4% by weight titanium and is approximately 14.5% by weight of magnesium.

Traditional Ziegler-Natta catalysts may also be used with one or more external donors. Generally such external donors act as stereoselective control agents to control the amount of atactic or non-stereoregular polymers produced during the reaction, thus reducing the amount of xylene solubility. Examples of external donors include organosilicon compounds such as cyclohexylmethyl dimethoxysilane (CDMS), dicyclopentyl dimethoxysilane (CPDS) and diisopropyl dimethoxysilane (DIDS). External donors, however, can reduce catalytic activity and tend to reduce the melt flow of the resulting polymer.

Metallocene catalyst system

Another catalyst system useful for polymerizing propylene is based on metallocenes. However, unlike Ziegler-Natta catalysts, metallocenes have not traditionally been used in bulk loop reactors, especially in bulk loop reactors that produce commercial quantities of polypropylene homopolymers and / or copolymers. Did. Metallocenes are generally specified as coordination compounds which introduce one or more cyclopentadienyl (Cp) groups (substituted or unsubstituted, different or identical) coordinated with the transition metal via π bonds. Cp groups also include substitutions by straight, branched, or cyclic hydrocarbyl radicals, and preferably to form ring structures comprising other adjacent ring structures, such as indenyl, azurenyl and florenyl groups. Substitutions by cyclic hydrocarbyl radicals. These additional ring structures may be unsubstituted or substituted by hydrocarbyl radicals and the preferred C1-C20 hydrocarbyl radicals. Metallocene compounds may be used as activators and / or promoters (described in more detail below) or as reaction products of activators and / or promoters, for example methylaluminoxane (MAO) and optionally trialuminum compounds (TEAL). , TMA and / or TIBAL) can be combined with an alkylation / scavenging agent. Various types of metallocenes are known in the art. Typical supports may be such as talc, inorganic oxides, clay and clay minerals, ion exchange laminated compounds, diatomaceous earth, silicates, or zeolites, or resinous support materials such as polyolefins. Specific inorganic oxides include silica and alumina and are used alone or in combination with other inorganic oxides such as magnesia, titania, zirconia and the like. Non-metallocene transition metal compounds such as titanium tetrachloride are also introduced into the supported catalyst component. The inorganic oxide used as the support has a surface area of 30-600 microns, preferably 30-100 microns, 50-1000 m ² / g, preferably 100-400 m ² / g, 0.5-3.5 cc / g, preferably 0.5 -Has a pore volume of 2 cc / g.

Any metallocene can be used in the practice of the invention. As used herein, unless otherwise indicated, "metallocene" includes a single methanelocene component or two or more metallocene components. Metallocenes are typically bulk ligand transition metal compounds represented generally as follows.

[L] mM [A] n

Where L is a bulk ligand, A is a living group, M is a transition metal, and m and n are such that the prime valence corresponds to the transition metal valence.

Ligands L and A may be bridged to each other, and if two ligands L and / or A are present, they may be bridged. The metallocene compound may be a pre-sandwich compound having two or more ligands L which may be a cyclopentadienyl ligand or a cyclopentadiene induced ligand, and one ligand that may be a cyclopentadienyl ligand or a cyclopentadiene induced ligand It may be a semi-sandwich compound having L. The transition metal atoms may be group 4, 5 or 6 transition metals and / or metals from the lanthanides and actinides. Zirconium, titanium, and hafnium are preferred. Other ligands may be bound to the transition metal, for example living groups, for example, hydrocarbyl, hydrogen or other monovalent ligands are anionic ligands. For example, bridged metallocenes can be described by the following general formula.

RCpCp'MeQn

Me represents a transition metal element, and Cp and Cp 'each represent a cyclopentadienyl group, which may be the same or different and may be substituted or unsubstituted, and Q is an alkyl or other hydrocarbyl or hydrogen group, n May be a number ranging from 1 to 3, and R is a structural bridge extending between cyclopentadienyl rings. Metallocene catalysts and metallocene catalyst systems for producing isotactic polyolefins are disclosed in US Pat. Nos. 4,794,06 and 4,975,403, all of which are incorporated herein by reference. These patents disclose stereorigid metallocene catalysts that polymerize chiral, olefins to form isotactic polymers, and are particularly useful for the polymerization of high isotactic polypropylene.

Suitable metallocene catalysts are described, for example, in US Pat.

4,530,914, 4,542,199, 4.76991 million, 4,808,561, 4,871,705, 4,933,403, 4,937,299,5,017,714, 5,026,798, 5,057,475, 5,120,867, 5,132,381, 5.15518 million, 5,198,401, 5,278,199, 5,304,614, 5.3248 million, 5,350,723, 5.39179 million, 5,436,305, 5,510,502, 5,145,819, 5,243,001, 5,239,022, 5,329,033, 5296434, 5276208, 5672668, 5304614, 5374752, 5510502, 4931471, 5532396, 5543373, 6100214, 6228795, 6.12423 million, 6114479, 6117955, 6087291, 6140432, 6245706, 6194341, 6399723, 6380334, 6380331, 6.38033 million, 6,380,124, 6,380,123, 6,380,122, 6,380,121, 6,380,120, 6,376,627, 6,376,413, 6,376,412, 6,376,411, 6,376,410, 6,376,409, 6,376,408, 6,376,407, 5,635,437, 5,554,704, 6,218,558, 6,252,097, 6,255,549, 6,255,549 576,970; And 611,773; And WO 97/32906; 98/014585; 98/22486; And 00/12565, each of which is hereby incorporated by reference in their entirety.

Metallocene activator

Metallocenes can be used with several types of activators to make the active catalyst system. The term "activator" is defined herein as any compound or component, or combination of compounds or components, capable of enhancing the ability of one or more metallocenes to polymerize olefins into polyolefins. Alkylaluminoxanes such as methylalumoxane (MAO) are commonly used as metallocene activators. Alkylalumoxanes generally contain about 5 to 40 repeat units.

R

l

AlR ₂ and R-(-Al-O) x for linear types

R

l

R-(-Al-O) x cyclic type

Where R is C1-C8 alkyl including mixed alkyl. Particular preference is given to compounds in which R is methyl. Alumoxane solutions, in particular methylalumoxane solutions, are available from commercial vendors as solutions with varying concentrations. There are a variety of alumoxane recipes, U.S. Pat. , Non-limiting examples such as EP-A-0 594 218 and WO 94/10180, all of which are incorporated herein by reference. (Unless otherwise indicated, the term "solution" is referred to as a suspension. Means a mixture containing.)

Ionization activators can also be used to activate the metallocenes. These activators are neutral or ionic and are also compounds such as tri (n-butyl) aluminum tetrakis (pentafluorofenyl) borate, which ionizes neutral metallocene compounds. Such ionizing compounds may include active protons or other cations that are bound but not coordinated or merely loosely coordinated with the residual ions of the ionizing compound. Combinations of activators can also be used, for example a combination of alumoxane and ionization activator, see WO 94/07928.

Techniques for ion catalysts for coordination polymerization comprising metallocene cations activated by non-coordinating anions are described in the earlier arts in EP-A-0 277 003, EP-A-0 277 004 and US 5,198,401 and WO-A-92. / 00333, which is incorporated herein by reference. These indicate a preferred preparation where metallocenes (bisCp and monoCp) are hydrogenated by anionic precursors so that the alkyl / hydride groups are extracted from the transition metals to be cationic and charge-balanced by non-coordinating anions. Suitable ionic salts include tetrakis-substituted borates or aluminum salts having fluoride aryl- members such as phenyl, biphenyl and naphthyl.

The term "non-coordinating anion" ("NCA") refers to an anion that is not coordinating to the cation or remains only weakly coordinating with the cation so that it can be sufficiently substituted by a neutral Lewis base. "Compatible" noncoordinating anions are those that do not deteriorate neutral when the initially formed complex decomposes. Moreover, anions do not transfer anion substituents or fragments to cations such that they form neutral by-product metallocene compounds and neutral by-products from the anions.

The use of ionizing ionic compounds which can produce active metallocene cations and uncoordinated anions but does not contain active protons is also known. See, for example, EP-A-0 426 637 and EP-A-0 573 403, incorporated herein by reference. An additional method of making ionic catalysts is using ionized anion precursors such as tris (pentaflofenyl) borane, which are initially neutral Lewis acids but form cations and anions during ionization reactions with metallocene compounds, EP-A-0 See 520 732, incorporated herein by reference. Ion catalysts for addition polymerization can also be prepared by oxidizing a metal center of a transition metal compound with an anion precursor containing a metal oxidizer together with an anion group. See EP-A-0 495 375, incorporated herein by reference.

If the metal ligand comprises a halogen moiety that is not ion extractable under standard conditions (e.g. biscyclopentadienyl zirconium dicloroids), these may be lithium or aluminum hydrides or alkyl, alkylalumoxanes, Grignard reagents and the like. It can be converted through a known alkylation reaction with the same organometallic compound. EP-A-0 500 944 and EP-A1-0 for in situ processes describing the reaction of an alkyl aluminum compound with a dihalo-substituted metallocene compound with or prior to the addition of the active anion compound. See 570 982, incorporated herein by reference.

Preferred methods for supported ion catalysts comprising metallocene anions and NCAs are described in U.S. Patent No. 5,643,847, filed November 2, 1998, U.S. Patent Application No. 09184389, filed November 2,1998. 09184389, incorporated by reference in its entirety. When using the support component, these NCA support methods generally involve the use of neutral anion precursors that are Lewis acids that are sufficiently strong to react with the hydroxyl reactive functionality present on the silica surface so that the Lewis acids are covalently bonded.

Additionally, the activator for the metallocene supported catalyst composition is NCA, preferably NCA is first added to the support composition followed by the addition of the metallocene catalyst. When the activator is MAO, preferably the MAO and metallocene catalysts are Dissolve together in solution. The support is then contacted with a MAO / metallocene catalyst solution. Other methods and order of addition will be apparent to those skilled in the art.

Bulk loop reactor

An embodiment of a bulk loop reactor system 10 suitable for propylene polymerization using one or more conventional Ziegler-Natta catalysts is described in FIG. 1. Bulk loop reactor system 10 includes an upstream catalyst mixing and injection system 200, a polymer recovery system 400 downstream of loop reactor 300, and a gas phase reactor 500 with a pair of loop reactors 300. . The bulk loop reactor system may comprise a single loop reactor or a single gas phase reactor or a plurality of loop reactors or a plurality of gas phase reactors or any combination thereof, including one or more olefin polymerization reactors, for example other propylene polymerization reactors. The bulk loop reactor 300 may further include a propylene feed pipe 300B and a comonomer (eg ethylene) feed pipe 300C.

The catalyst mixing and injection system 200 includes a mixing vessel 202. The mixing vessel 202 includes a mixing paddle 204 and a heating jacket 206. High molecular weight mineral oil and Ziegler-Natta catalysts are introduced into the mixing vessel 202. Generally, high molecular weight oils are heated to reduce the viscosity of the mineral oil so that the mixing paddle 204 can sufficiently mix the catalyst and the high molecular weight oil (from about 30 ° C. to at least 90 ° C., depending on the type of mineral oil used. The heated mixture of high molecular weight mineral oil and catalyst is then passed through conduit 208 to injector 210 where it is cooled to form a "paste". The paste enters the conduit 212 during the compression stroke of the plunger 211 and into another mixing vessel 214 where a promoter, such as TEAL and one or more electron donors, is mixed with the paste by the mixing paddle 216. do. The resulting mixture of catalyst, promoter and electron donor exits mixing vessel 214 via conduit 218 and is fed by pump 220 to pre-polymerized loop reactor 222 containing liquid propylene monomer. The polymerization temperature in the pre-polymerization loop reactor 222 is from -10 ° C to + 10 ° C and is controlled by the cooling jacket 223. The propylene polymer granules are formed by propylene polymerization upon contact between the catalyst / procatalyst and the liquid propylene monomer, all of which are circulated in the pre-polymerization loop reactor by the purifying pump 224.

The pre-polymerization cycle time may last from 7 to at least 30 minutes, preferably from 15 to 20 minutes, before the propylene polymer granules are transferred through the conduit 226 to the first loop reactor 302 containing the liquid propylene monomer. have. Circulation pump 304 circulates propylene granules and liquid propylene monomer in first loop reactor 302. Propylene polymerization continues in the first loop reactor and the propylene polymer granules increase in size. The first loop reactor cycle time may last for 20 to at least 95 minutes, preferably 30 to 50 minutes, before the propylene polymer granules are transferred to the second loop reactor 308 through the conduit 306. The temperature range in the first and second loop reactors, 302 and 308, respectively, can be 66 to 77 ° C. and is controlled by the cooling jacket 310. Circulation pump 312 circulates propylene granules and liquid propylene monomers in a second loop reactor. The second loop reactor cycle time lasts 10 to at least 60 minutes, preferably 20 to 50 minutes, before the propylene polymer granules are transferred to the polymer recovery system 400 through the conduit 313. Generally, if no further olefin polymerization is desired, the catalyst is deactivated or “killed” prior to entering the polymer recovery system 400.

Heating column 402 receives propylene polymer granules from conduit 312. When sufficient heat is applied to the propylene polymer granules and enters the flash tank 406 from the conduit 404, a significant portion of the liquid propylene monomer with the propylene polymer granules is evaporated and thus separated from the granules. The gaseous polypropylene and polymerization byproduct portions are extracted from the flash tank 406 through conduits 408. This propylene is recompressed and filtered to remove impurities and other contaminants that react back with the catalyst system and return to the loop reactor 300.

The propylene polymer granules exit the flash tank 406 through the conduit 410 and are led to an extruder that is processed into pellets. Alternatively, if further polymerization with one or more monomers, such as ethylene, is required, the propylene polymer granules exiting the flash tank 402 through the conduit 412 can be transferred to the gas phase reactor 500. The propylene polymer granules exit gas phase reactor 500 through conduit 502 and can be directed to an extruder to be processed into impact polypropylene copolymer pellets. During pelletization, one or more other materials, such as stabilizers, UV blockers, antistatic agents and / or pigments, may be kneaded with the propylene polymer granules.

Another bulk loop reactor system 12 suitable for propylene polymerization with one or more conventional Ziegler-Natta catalysts is shown in FIG. 2. Bulk loop reactor system 12 represents a bulk loop reactor system (except that system 12 represents a broader polymer recovery system 300A and does not represent a gas phase reactor or a pre-polymerization loop reactor 222). Similar to 10). In some instances, but not all, but in most cases, the active catalyst present in the propylene polymer granules leaving the loop reactor 300A through conduit 314 may be deactivated before entering wash column 414. Generally, the propylene polymer granules are separated from the liquid propylene and wash column 414. In some instances, additional liquid propylene coming into or near the bottom of wash column 414 passes through the phases holding the propylene polymer granules. A portion of the liquid propylene and polymerization by-product exits wash column 414 through conduit 415 and is sent to distillation vessel 416. The distillation vessel separates liquid propylene from polymerization byproducts such as atactic polyflopropylene.

Remaining propylene polymer granules, propylene monomer, and polymerization byproducts leave wash column 414 through conduit 417 and enter heating column 418. The propylene polymer granules leave the washing column 414 either continuously or batchwise. Sufficient heating is applied to the propylene polymer granules and, when entering the flash tank 420, a significant portion of the liquid propylene monomer accompanying the propylene poly granules evaporates and is separated from the granules. Gas phase propylene and other polymerization byproducts are extracted from flash tank 42 through conduit 422. The gaseous propylene is compressed by the regeneration compressor 424 and sent to the distillation vessel 416 through the conduit 426. The liquid propylene monomer exits the distillation vessel through conduit 427 and can be transferred to one propylene feed processor 428, where propylene can be filtered before returning to loop reactor 300A as above. The propylene polymer granules exit the flash tank 420 through the conduit 430 and enter the purge column 432. Upon leaving the purge column, the propylene polymer granules can be directed to an extruder to be processed into pellets as described above.

Transition to Ziegler-Natta's Metallocene Bulk Loop Reactor

It is known that metallocene catalyst systems can also be used to produce propylene polymers in bulk loop reactors. However, in some instances, the Ziegler-Natta catalyst system and / or components thereof may be incompatible with the metallocene catalyst system and / or components thereof. In addition, certain conditions and equipment designs of bulk loop reactor systems suitable for propylene polymerization with one or more Ziegler-Natta catalyst systems may be inappropriate or less suitable for the polymerization of propylene with one or more metallocene catalysts. Therefore, when there is a transition between a Ziegler-Natta catalyst system and a metallocene catalyst system for the production of polypropylene in a conventional loop reactor and a conventional loop reactor system, one or more bulk loop reactors may be operated in operation and / or It is desirable to take changes in the design of the bulk loop reactor system elements. These and other changes will be mentioned in more detail.

Catalyst Mixing and Injection System

Referring to FIG. 1, traditionally, Ziegler-Natta catalysts are dry-mixed in the mixing vessel 202 with a high molecular weight mineral oil in a ratio of about 1: 2. In many instances, drying of the metallocene catalyst and in particular of the supported metallocene catalyst can impact its productivity (degeneration from impurities such as oxygen or moisture during the heating and drying process). It is desirable to store and transport the supported metallocene catalyst from the low molecular weight mineral Auryl slurry to the bulk loop reactor. The weight percent of the metallocene catalyst system supported in the mineral oil slurry can vary from 1 to at least 50 weight percent, preferably from 5 to 30 weight percent.

If a high molecular weight mineral oil paste is used to carry the metallocene catalyst system, the temperature in the mixing vessel 200 must be sufficiently reduced so that the metallocene catalyst is not deactivated during mixing with the mineral oil. In general, thermal deactivation of the metallocene catalyst can be avoided by heating the metallocene at 60 ° C. or lower, preferably 30 ° C. or lower. For this reason, heating, which is opposed to simple heating, is preferred by adding a solvent, for example nucleic acid, to lower the viscosity of the high molecular weight mineral oil. Once the metallocene catalyst is substantially dispersed in the mineral oil, the solvent is vacuum extracted and the resulting "paste" is sent to injector 210.

If the catalyst mixing system 200 used in the Ziegler-Natta catalyst system can also be used in the metallocene catalyst system, the remaining Ziegler-Natta catalyst under the conditions in which the metallocene polypropylene is generally produced (no hydrogen, no external donors) Can produce high molecular weight adactic polypropylene. Such high molecular weight materials can be the source of gels in metallocene polypropylene. In many instances, residual electron donors can act as a strong position for the metallocene catalyst. Therefore, it is desirable to clean the mixing vessel 202 and all conduits related to such Ziegler-Natta catalysts and residual electron donors. In addition, such Ziegler-Natta catalysts and residual electron donors may be present in other elements of the bulk loop reactor system, such as in the propylene monomer circulation element, so that other elements of the bulk loop reactor system may also be washed and It is desirable to purge. For example, the catalyst mixing system 200 may be cleaned by opening the system and introducing mineral oil at high pressure. Preferably, the catalyst mixing system 22 can be similarly washed when transitioning the catalyst mixing system from the metallocene catalyst to the Ziegler-Natta catalyst.

Alternatively, a separate catalyst mixing system can be used for the metallocene catalyst (described in more detail below and depicted in FIG. 3). In this case, cleaning of the catalyst mixing system 200 and / or urea of the Ziegler-Natta catalyst system before introduction of the metallocene catalyst catalyst system may be avoided. However, washing other elements of the bulk loop reactor with mineral oil to purge the elements of the Ziegler-Natta catalyst system and / or their elements is expensive and time consuming. Optionally, other elements may be washed or purged by one or more methods or combinations thereof.

In one embodiment, the Ziegler-Natta catalyst circulating in the loop reactor can be deactivated and subjected to conventional discharge after 3 to 5 loop residence time or 3 to 10 hours (1 to 2 hours / residual time). The deactivated catalyst is substantially removed. If the electron donor is present with the Ziegler-Natta catalyst, the Ziegler-Natta catalyst is deactivated as above, but in order to clean the loop reactor and its elements, for example the polymer recovery system of the electron donor, the bulk loop reactor system is It may be operated for an additional time, generally 5 to 10 hours, to purge the donor component.

In another embodiment, if the Ziegler-Natta catalyst system comprises an electron donor, the catalyst system may be transferred to a non-electron donor Ziegler-Natta catalyst system. In this case, propylene polymer production continues as the electron donor is purged in the bulk loop reactor system. Prior to transition to the metallocene catalyst system, the Ziegler-Natta catalyst system is deactivated and the reactor is purged for 3 to 5 loop residence times. As such, in addition to producing propylene polymers in the electron donor purge, this loop reactor cleaning method can be accomplished in substantially less time than the above method.

In another embodiment, the Ziegler-Natta catalyst can be deactivated and a metallocene catalyst system is introduced into the bulk loop reactor system. In this case, the loop reactor and polymer recovery system can be purged by the production of metallocene propylene. This method can take from 8 hours to 24 hours to fully purge the loop reactor system and / or its components of the Ziegler-Natta catalyst.

Upon transition from the metallocene catalyst system to the Ziegler-Natta catalyst system, the procedure can be used to purge the relevant elements of the loop reactor and the metallocene catalyst system. The time taken to transfer from the metallocene catalyst system to the Ziegler-Natta catalyst system is similar to the time taken to transfer from the Ziegler-Natta catalyst system to the metallocene catalyst system. As such, in one embodiment, the metallocene catalyst system can be deactivated and purged from the elements associated with the loop reactor. In another embodiment, a non-electron donor Ziegler-Natta catalyst system can be introduced allowing for continued propylene polymer production while purging the associated elements of the loop reactor and the metallocene. In another embodiment, the metallocene catalyst system may be deactivated followed by the introduction of a Ziegler-Natta catalyst system into the loop reactor.

In FIG. 3, two metallocene catalyst mixing systems are shown in FIGS. 3A and 3B. Both systems do not require the use of a pre-polymerized loop reactor prior to introducing the metallocene catalyst into the loop reactor 300, and both systems can be used with the pre-polymerized loop reactor.

The metallocene catalyst mixing system 316 shown in FIG. 3A is a mixing vessel with a mixing paddle 320 for sufficient agitation and maintenance of sufficient dispersion in the mineral oil slurry of the metallocene catalyst and the promoter. 318. The weight percent metallocene catalyst in the mineral oil is generally from 1 to 50, preferably from 5 to 30. The metallocene catalyst slurry is transferred to valve 324 through conduit 322. As the valve 324 opens, a portion of the slurry enters the conduit 326. When valve 324 is closed, slurry flow to conduit 326 is stopped. Generally, the frequency of slurry introduction into conduit 326 is 1 to 10 times per minute. The amount of slurry in each "slug" can be from 10 to 50 milliliters.

Conduit 326 intersects with conduit 328 at junction 327. Conduit 328 may be used to blend TEAL or TIBAL with metallocene catalysts / catalysts and TEAL in amounts of TEAL to scavenger and / or cocatalyst, e.g., support catalyst. Or to a junction point 327 in "line contact". Optionally, the metallocene catalyst and cocatalyst may be introduced separately into the bulk loop reactor. In this embodiment, there may be a loss of activity of the catalyst and a morphology loss of the propylene polymer granules. However, when using two catalyst systems, the catalyst is scavenged, e.g., TEAL (in mixing vessel 202, mixing vessel as shown in FIG. 1 or conduit 330 in FIG. (332) and / or downstream) is preferably in line contact. In this case, TEAL is readily available as an impurity scavenger, thus protecting the catalyst during initial contact with propylene. Additionally, pure TEAL can be used, while solvents such as hexane or C4 to C20 hydrocarbons reduce the viscosity of the mineral oil surrounding the catalyst and thus enhance the polymerization when TEAL is miscible with the solvent. Relative to improve the dispersion of propylene relative to.

When a conventional Ziegler-Natta catalyst system is used, the addition of TEAL (TEAL lbs. To lbs. Of supported catalyst in the range of 5: 1 to 15: 1) increases the activity of the catalyst. In a metallocene catalyst system, a minimum amount of TEAL and / or TIBAL (lbs of TEAL or TIBAL for lbs. Of supported catalyst is 1: 4 lbs. Of TEAL or TIBAL for lbs. Of supported catalyst is 4 In the range up to: 1 and preferably in lbs. Of TEAL or TIBAL to lbs. Of supported catalyst is 1: 1) preferred as a scavenger and in the above line contact. Generally, however, scavengers, such as excess of TEAL (lbs of TEAL relative to lbs. Of supported catalyst is greater than 4: 1), reduce catalytic activity and increase fouling.

The line contact time of the Ziegler-Natta catalyst is several minutes, ranging from 5 to 15 minutes. In the metallocene catalyst, the line contact time is preferably less than 1 minute, more preferably less than 30 seconds, more preferably 15 seconds or less. For example, the diameter of the conduit 330 is 0.5 inches, the line length of the conduit 330 is 15 feet, and the TEAL solution is 12 lbs./hr (5% by weight diluted in hexane) at the junction 327. The metallocene catalyst / mineral oil slurry enters the junction 327 at 6 gals / hr and the flow time of the conduit 330 is about 15 seconds.

Conduit 330 downstream of junction 327 provides a metallocene catalyst / promoter to junction 332, where the propylene monomer and active metallocene catalyst / promoter carried by conduit 334 are mixed, A certain distance of conduit 336 is moved before entering the loop reactor 300. Since propylene polymer polymerization is generally initiated at or at junction 332, it is desirable to transfer the polymerized metallocene catalyst into the reactor before clogging of conduit 336 occurs by accumulation of propylene polymer granules. . Depending on the size of the conduit 336 and the flow rate of the material therein, transfer from the junction point 332 to the bulk loop reactor is about 1 minute or less, preferably 30 seconds or less, more preferably 15 seconds or less, Most preferably from 10 to 0.001 seconds. For example, if the diameter of the conduit 336 is 0.5 inches, 15 feet long, the propylene flow rate in the conduit 334 is about 10 gal / min, and the flow in the conduit 336 is about 5 m / s. In the conduit 336, the polymerization time is about 1 second.

In order to reduce clogging of the conduit 336 by the propylene polymer granules, the metallocene / procatalyst mixture and propylene may be mixed under conditions where the rate of polymerization in the conduit 336 is slower than the rate of polymerization in the bulk loop reactor 300. have. This can be done, for example, by cooling one or more metallocenes, cocatalysts and / or propylene components after one or more of them have been blended. Generally one or all such components may be cooled to a temperature of −10 ° C. to + 10 ° C. For example, maintaining a flow rate from 0.3 m / s to 10 m / s in conduit 336 also reduces the risk of clogging. The flow rate in conduit 336 may be a factor of the individual flow rates of the individual components. Preferably, the flow rate in the conduit 326 of the metallocene catalyst and in the conduit 328 of the promoter is slower than the flow rate of propylene in the conduit 334. Different flow rates enhance the mixing of the metallocene catalyst upon contact with propylene.

Referring now to FIG. 3B, the metallocene catalyst mixing system 340 is substantially comprised of the metallocene catalyst mixing system 316, the pump 342, preferably the membrane pump 150 l / hr, 0- 80 barg.) Is similar except that it has an upstream check valve 344 and a downstream check valve 346 instead of the valve 324 of FIG. 3A. In this case, the catalyst, cocatalyst, and propylene are introduced into the bulk loop reactor in a continuous form than the valve 324 (FIG. 3) (eg, in an amount ranging from 4 to 16 milliliters of slurry slug frequency, 60 to 120 times per minute). ) Can be introduced. In addition to the more continuous and / or more frequent dosing, the volume of less catalyst and cocatalyst introduced into the bulk loop reactor can minimize the fluctuations in reactor temperature caused by the polymerization.

Referring now to FIG. 4, a quill 338 having portions defining a quill body 339, a quill lumen 340, a quill surface 342, an upstream end 343, and a downstream end 344. It may be desirable to install. The upstream end 343 of the quill 338 may be integrally molded with the conduit 330 or may be submerged in the conduit 330 by, for example, an engagement thread, flange or welding. Quill lumen 340 is in communication with conduit 330 in fluid. Quill body 339 extends from conduit 330 into junction 332. Preferably, the external dimension of the quill body 339 is such that the flow of liquid propylene (shown as a continuous arrow) entering the conduit 334 through the conduit 334 to the junction 332 as the liquid propylene proceeds toward the conduit 336 It is tailored to contact the outer surface 342 of 338. In addition, the length of the quill body 339 is sufficiently long such that the downstream end 344 ends downstream of the junction 332, preferably ends in the conduit 336, and more preferably with the flange 346. Termination in connected conduit 336. As such, the flow of catalyst (shown as broken lines) enters conduit 336 and mixes with the liquid propylene flow downstream of junction 332 and its associated flange / weld seams. In this case, propylene polymerization at and / or in junction 332 is reduced and / or eliminated, in turn the opportunity for catalyst particles to accumulate in and / or near the connecting flange 346 and their gaskets (not shown). Reduce and / or eliminate.

Additionally, the conduit and junction internal lumen surfaces described in FIGS. 3A, 3B and 4 may have any gaps, bumps, protrusions, grains or other similar structures, or metallocene catalyst particles and / or propylene polymer granules within and / or within the lumen surface. Or it is desirable that there are no or minimal shapes that accumulate therein and prevent it from being swept into the reactor by flow in conduit 336. Such gaps, ridges, and protrusions may be caused by, for example, non-alignment of gaskets, welds, or fringes. Any particles or granules that do not sweep into the reactor continue to grow and / or cause accumulation of other particles, both or both of which can cause blockages or blockages in the lumen. Therefore, the surface defining these lumens should be polished, for example electrically polished, and the gasket should be selected to avoid gaps in the flange. For example, the portion defining the surface and / or lumen preferably has a roughness value of 0 rms to 120 rms, preferably between 8 rms and 20 rms as measured by techniques known to those skilled in the art.

Loop reactor

In general, when using a conventional Ziegler-Natta catalyst system compared to using a metallocene catalyst system, there is a minimal change made in the reactor. However, there are some design considerations of the preferred loop reactor.

For example, the bulk density of the propylene polymer granules made by the Ziegler-Natta catalyst system may vary compared to the bulk density of the propylene polymer granules made by the metallocene catalyst system. However, in some instances, when making a metallocene propylene random copolymer with ethylene, the bulk density of the metallocene polymer granules may be similar to the propylene homopolymer granules formed by conventional Ziegler-Natta catalyst systems. For example, the bulk density is for example 18 lbs./cu.ft. (0.30 g / cc for copolymers at 25 lbs./cu.ft. (0.45 g / cc) for homopolymers. Can fall). Low bulk density (ie higher specific volume, or volume / lbs.) Is generally more difficult to circulate in the reactor. As such, reactor purifying pump impellers and motors must be designed with higher horsepower loads.

When using a conventional Ziegler-Natta catalyst system compared to using a metallocene catalyst system, another variant is the addition of an anti-fouling agent. In some instances, the formation of a polymer coating may occur over a period of time, either in a loop reactor or in a product take-off line from the reactor. The use of antifouling agents can be put in place to prevent these polymer coatings from forming. Anti-fouling agents may be added to the propylene feed to the reactor. Or it is injected such that an antifouling agent is also present in the catalyst mixing and injection system, thus reducing the risk of conduit blockage.

In some instances, the use of antifouling agents reduces the activity of the metallocene catalyst. Examples of suitable antifouling agents are the products of dinonylnaphthyl sulfonic acid based antifouling agents, for example Staids 450 conductivity enhancers, Octel Starreon, LLP (hereinafter referred to as "Stadis"). Stadis may be used in propylene feed (conduit 300B (FIG. 1)) to the reactor at a concentration of about 0.1 ppm to 5 ppm, or may be used in a direct catalyst mixing and injection system at such concentration. However, the direct mixing of the antifouling agent upstream of the catalyst mixing and injection system upstream of the propylene injection (conduit 334, FIGS. 3A and 3B) may be achieved by direct injection of the antifouling agent or catalyst into the reactor through the propylene conduit 300B. This results in higher concentrations of the antifouling agent coming into contact with the catalyst than propylene injection (conduit 334) or the introduction of the antifouling agent downstream in the mixing and injection system. Contacting the catalyst with a higher concentration of antifouling agent in the catalyst mixing and injection system can increase the level of catalyst deactivation. These may, for example, inject a portion of the antifouling agent stream upstream of the point of contact of the catalyst with propylene in the catalyst mixing system, or all or the antifouling agent at the point of contact of propylene and the catalyst in the catalyst mixing and injection system, or Or a portion of the antifouling agent at a point downstream of the propylene injection conduit 334 in the catalyst mixing and injection system, or a propylene feed in fluid communication with the propylene injection conduit 334 Injecting into conduit 300B may be addressed by a number of methods, such as allowing some of the antifouling agent to enter the catalyst mixing and injection system through the propylene injection conduit 334.

Other possible antistatic agents can be used, such as ethylene oxide based antifouling agents. Examples of ethylene oxide / propylene oxide block copolymer antifouling agents are sold under ICI, BASF, respectively, under the trade name Synperonic or Pluronic Products. Synperonic or Pluronic antifouling agents prevent fouling as effectively as Stadis, with the added benefit of minimizing the loss of catalyst activity in the concentration range of 2 ppm to 100 ppm.

It has also been observed that antifouling agents tend to continue in the reactor (i.e., the antifouling effect persists for some time after the stoppage of the antifouling agent). Thus, initially, the antifouling agent is supplied at an initial level of 5 ppm to 10 ppm, and then after a period of time (at least 10 minutes to 10 minutes), the anti-fouling agent is reduced to a second level ranging from 2 ppm to 5 ppm. It is preferable to supply the fouling agent. The reduced supply of antifouling agent into the bulk loop reactor reduces the loss of metallocene catalyst activity, thus increasing the propylene polymer production.

A comparison between the Ziegler-Natta catalyst system (Z-N) and the metallocene catalyst system (MCN), dilution, density and residence time in the bulk loop reactor is provided in Table 1.

First loop reactor unit Z-N MCM Propylene supply t / h 31 34-38 density g / l 555 540-560 solid weight % 50 45-55 Contribution Final production% 62 65-69 Temperature ℃ (℉) 70 (158) 68-75 PP production t / h 15.5 15-18 Residence time min 43 35-45 Second loop reactor unit Z-M MCM Propylene supply t / h 16 10-12 density g / l 540 535-550 solid weight % 46 45-55 Contribution Final production% 38 31-35 Temperature ℃ (℉) 70 (158) 68-75 gun unit Z-N MCM PP production t / h 25 20-30 Propylene supply t / h 47 40-50 Residence time min 68 55-80

In some instances, the electrical consumption of the reactor circulation pump may be lower for the metallocene catalyst system compared to the Ziegler-Natta catalyst system. Table 2 compares MCM and Z-N for a double loop reactor. Less kWh means higher circulation rate. This is typical for propylene polymer granules having an average particle size of about d50.

Reactor 1 unit Z-N MCM density g / l 555 550 Circulating pump KWh 215 198 Reactor 2 unit Z-N MCM density g / l 540 540 Circulating pump KWh 248 228

In these examples, one of the catalyst systems, for example a metallocene catalyst system, produces a propylene polymer that has a lower melting point than the propylene polymer produced by another catalyst system, such as Ziegler-Natta catalyst system. Adjustment is preferred. For example, the metallocene polypropylene homopolymer has a melting point of, for example, 150 ° C., and when the conventional Ziegler-Natta polypropylene homopolymer has a melting point of, for example, 165 ° C., the polymer recovery system has a lower temperature. Can be adjusted. Polymer recovery systems for Ziegler-Natta random copolymers and metallocene PP homopolymers having a melting point of 150 ° C.

Flash T °: 65-70 ° C (instead of 90 ° C) for metallocene PP homopolymer

Flash p: <1.7 barg

N2 T ° in fluid bed dryer: 105-110 ° C (instead of 120 ° C) for metallocene PP homopolymer

ATMER antistatic, ICI US products reduce and / or eliminate the activity of Ziegler-Natta catalysts or metallocene catalyst systems in a flash line of 5 kg / h (lower than for ZN to avoid electrostatic problems in cyclones) ).

Although the invention may be shown in only some forms, it will be apparent to those skilled in the art that this is not limited thereto and is sensitive to various changes and modifications without departing from the scope of the invention.

Claims (17)

Introducing a first frequency of an amount of metallocene catalyst having a second temperature range into the bulk loop reactor from the first catalyst mixing system in communication with the bulk loop reactor; And Introducing a predetermined amount of Ziegler-Natta catalyst having a third temperature range from the second catalyst mixing system in communication with the bulk loop into the bulk loop reactor at a second frequency; Propylene polymerization method in a bulk loop reactor having a first temperature range comprising a. The method of claim 1 wherein the first frequency is higher than the second frequency. The method of claim 1, wherein the frequency of infusion is 60 to 120 times per minute. The method of claim 1 wherein the first temperature range is higher than the second temperature range. Contacting a quantity of supported metallocene catalyst with a first amount of scavenger before injecting the supported metallocene catalyst into the bulk loop reactor; And, Contacting an amount of the Ziegler-Natta catalyst with a second amount of scavenger greater than the first amount before injecting the Ziegler-Natta catalyst system into the bulk loop reactor; Propylene polymerization method in a bulk loop reactor comprising a. 6. The method of claim 5, wherein the first and second amounts of scavenger comprise an amount of TEAL. 6. The method of claim 5, wherein the first amount of scavenger and supported metallocene catalyst are present in a ratio of scavenger to supported metallocene catalyst in the range of 1: 4 to 4: 1. 6. The method of claim 5 wherein the second amount of scavenger and Ziegler-Natta catalyst system is present in a ratio of scavenger to Ziegler-Natta catalyst system in the range of 5: 1 to 15: 1. Directing the flow of metallocene to the junction; Directing the flow of propylene to the junction; And Maintaining a flow of a portion of the metallocene separated from the portion of the propylene stream at a distance to the junction of the downstream propylene stream; Method of contacting the flow of propylene and the flow of metallocene comprising a. 10. The process of claim 9, wherein the temperature range of the propylene flow is from-10 ° C to + 10 ° C. 10. The method of claim 9, wherein the flow rate downstream of the junction is from 0.3 m / s to 10 m / s. 10. The method of claim 9, further comprising directing the contacted flow of metallocene and propylene into the conduit under sufficient flow conditions such that the contacted flow has a residence time of 0.001 seconds to 1 second in the conduit. 13. The method of claim 12, wherein the conduit has an internal lumen, wherein the portions for the internal lumen have a roughness value of 0 to 120 rms. Injecting an amount of antifouling agent into the catalyst mixing system; And Injecting the product portion of the preceding step into the bulk loop reactor; Method for introducing a predetermined amount of antifouling agent to the bulk loop reactor comprising a. 15. The method of claim 14, wherein the antifouling agent is a member kneaded with a single or other member selected from the group consisting of Stadis 450 conductivity enhancer, synferonic antifouling agent, and pluronic antifouling agent. 15. The method of claim 14, wherein a portion of the antifouling agent injected into the catalyst mixing system is introduced into or downstream of the portion where the flow of propylene and the flow of catalyst are in contact in the catalyst mixing system. The method of claim 16, wherein the amount of antifouling agent injected into the catalyst mixing system is reduced over time.